/*
ajax请求函数模块
返回值: promise对象(异步返回的数据是: response.data)
 */
// document.write("<script type='text/javascript' src='/js/axios/index.js'></script>");
// document.write("<script type='text/javascript' src='/springbootmb/js/axios/index.js'></script>");
 function ajax (url, data={}, type='GET') {
   type = type.toUpperCase();
    return new Promise(function (resolve, reject) {
        // 执行异步ajax请求
        let promise
        if (type === 'GET') {
            // 准备url query参数数据
            let dataStr = '' //数据拼接字符串
            Object.keys(data).forEach(key => {
                dataStr += key + '=' + data[key] + '&'
            })
            if (dataStr !== '') {
                dataStr = dataStr.substring(0, dataStr.lastIndexOf('&'))
                url = url + '?' + dataStr
            }
            // 发送get请求
            promise = axios.get(url)
        } else if(type === 'POST'){
            // 发送post请求
            promise = axios.post(url, data)
        }else if(type === 'PUT'){
            promise = axios.put(url, data)
        }else if(type === 'DELETE'){
            promise = axios.delete(url)
        }
        promise.then(function (response) {
            // 成功了调用resolve()
            resolve(response.data)
        }).catch(function (error) {
            //失败了调用reject()
            reject(error)
        })
    })
}
